1. Field of the Invention
The present invention relates to a dispersion comprising a vehicle and a modified pigment comprising a pigment having attached organic groups. The modified pigment has, when measured in an aqueous medium, a zeta potential of 0.0 mV at a pH of between about 5.0 and 11.0. Inkjet ink compositions and an inkjet consumable set are also disclosed.
2. Description of the Related Art
In general, pigments alone are not readily dispersible in liquid vehicles. A variety of techniques have been developed which can provide stable pigment dispersions. For example, dispersants can be added to the pigment to improve its dispersibility in a particular medium. Examples of dispersants include water-soluble polymers and surfactants. Pigment dispersions have applications in a variety of pigment-based ink compositions.
Recently, modified colored pigments have also been developed which provide ink compositions with improved properties, such as dispersibility. For-example, U.S. Pat. No. 5,851,280 discloses methods for the attachment of organic groups onto pigments including, for example, attachment via a diazonium reaction wherein the organic group is part of the diazonium salt. The resulting surface-modified pigments can be used in a variety of applications, such as inks, inkjet inks, coatings, toners, plastics, rubbers, and the like.
PCT International Publication No. WO 01/51566 describes a method of making a modified pigment by reacting a first chemical group and a second chemical group to form a pigment having attached a third chemical group. The first chemical group includes at least one nucleophile and the second chemical group includes at least one electrophile, or vice versa. These pigments are used in ink compositions and, in particular, inkjet ink compositions.
While these efforts provide modified pigments with improved properties, there remains a need for improved pigment-based dispersions and ink compositions.
The present invention relates to a dispersion comprising: a) a vehicle; and b) a modified pigment comprising a pigment having attached at least two organic groups, wherein the modified pigment has, when measured in an aqueous medium, a zeta potential of 0.0 mV at a pH of between about 5.0 and about 11.0. In a preferred embodiment, the dispersion is an inkjet ink composition.
The present invention further relates to a dispersion comprising: a) a vehicle; and b) a modified pigment comprising a pigment having attached at least one organic group, wherein the organic group comprises an anionic or anionizable group and a cationic or cationizable group, and wherein the modified pigment has, when measured in an aqeuous medium, a zeta potential of 0.0 mV at a pH of between about 5.0 and about 11.0. In a preferred embodiment, the dispersion is an inkjet ink composition.
The present invention further relates to an inkjet consumable set comprising a substrate having a surface pH of between about 4.0 and 8.0 and the inkjet ink compositions described herein.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.